When the temperature drops close to absolute zero, some substances undergo a sudden chemical change and become a "superconductor" with almost no resistance. The temperature at which matter begins to take on this strange "superconducting" property is called the critical temperature. Needless to say, the critical temperature of various substances is not the same.
You know, ultra-low temperatures are not easy to get, and people pay a huge price for it; The closer we get to absolute zero, the greater the cost. Therefore, our requirement for superconducting materials is, of course, the higher the critical temperature, the better.
There are many elements with superconducting properties, among which niobium has the highest critical temperature. Alloys made of niobium, with critical temperatures as high as 18.5-21 degrees absolute, are currently the most important superconducting materials.
A large portion of the world's niobium is used in the production of nickel, chromium and iron-based superalloys in pure metallic form or in the form of high purity ferric niobium and niobium nickel alloys. These alloys are used in jet engines, gas turbine engines, rocket components, turbochargers and heat-resistant combustion devices. Niobium forms a γ "phase in the grain structure of the superalloy. These alloys generally contain up to 6.5% niobium.
Niobium C-103 Alloy is a niobium alloy containing 89% niobium, 10% hafnium and 1% titanium, which can be used in liquid rocket propulsion nozzles, such as the main engine of the Apollo lunar module. The Apollo service module used another niobium alloy. Since niobium begins to oxidize above 400°C, a protective coating must be applied to its surface in order to prevent it from becoming brittle.
